Classes are the blueprints for creating objects in Java. A class defines the properties and behaviors that an object will have. For example, a Car class might define properties such as color, make, and model, and behaviors such as starting, stopping, and accelerating. Once a class is defined, objects can be created from it, each with its own set of values for the properties.

Objects are the fundamental building blocks of OOP in Java. An object is an instance of a class, which is a blueprint for creating objects. Every object has its own set of properties and behaviors, which are defined by its class. For example, a car object might have properties such as color, make, and model, and behaviors such as starting, stopping, and accelerating.

Inheritance is the process by which one class inherits properties and behaviors from another class. This allows you to create more specialized classes that share common properties and behaviors with their parent class. For example, you could create a SportsCar class that inherits properties and behaviors from the Car class, but also has additional properties and behaviors specific to sports cars.

Encapsulation is the concept of wrapping data and behaviors into a single unit, and hiding the implementation details from the outside world. This is achieved in Java through the use of access modifiers, such as public, private, and protected. By using these access modifiers, you can control which parts of a class are visible to the outside world.

Polymorphism is the ability of an object to take on many forms. In Java, this is achieved through the use of method overriding and method overloading. Method overriding allows a subclass to provide a specific implementation of a method that is already provided by its parent class. Method overloading allows a class to have multiple methods with the same name, but different parameters.